On Tue, Nov 22, 2022 at 02:24:51PM +0200, Vladimir Oltean wrote:

On Tue, Nov 22, 2022 at 09:38:43AM +0000, Russell King (Oracle) wrote:

quoted

88E1111 is the commonly used accessible PHY on gigabit SFPs, as this
PHY implements I2C access natively.

As a side question, I suppose it would be possible to put PHYs on copper
SFP modules even if they don't natively implement I2C access. In that case,
if configuration from the host is at all available, how does that happen,
is there some sort of protocol translator (I2C -> MDIO) on the module?

Modules that provide access to the PHY seem to do so on I2C address 0x56
and require specific I2C access patterns. I think the 88e1111 set a kind
of "standard" and many follow that or similar.

Some just don't give any kind of access to the PHY - for example, the
Mikrotik modules have an AR803x PHY on them, but there is no way to
access it.

Do you know of any part number for an I2C controlled MDIO controller?

I think many that don't use a microcontroller - for example, when
someone puts an 88x3310, bcm84881, the protocols are very similar but
timing may vary.

Some of the patches from Marek provided a different way - via the 0x50
or 0x51 "eeprom" addresses, accessing specific addresses with in those
spaces, and if I remember correctly, requiring a "password" to enable
access.

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